PENDLETON - About 60 people from a four-county region around the Oconee Nuclear Station gathered Wednesday night to hear from a nuclear power expert about the need for Duke Energy to take quicker, more decisive action to prevent flooding at the plant.

David Lochbaum of the Union of Concerned Scientists, a nuclear engineer who spent 17 years in private industry, said members of the public should press the media, federal regulators and elected representatives to step up attention to the issue.

The Oconee Nuclear Station is on the shore of Lake Keowee, a Duke Power reservoir built in the early 1970s to provide backup power and water supply to the reactors. Upstream, the energy giant also built Jocassee Dam to create a second reservoir that would guarantee water supplies.

Lochbaum said his concern is not that Duke or federal regulators are unaware of the risks at Oconee but that they are taking too long to respond.

He was speaking to members of a local Sierra Club group for their regular monthly meeting at the Unitarian Universalist church in Pendleton.

At the beginning of his discussion, Lochbaum showed photographs of flooding at the Fukushima plant in Japan that occurred in March 2011 after a record earthquake and tsunami struck the region. A 46-foot-tall wave washed over 13-foot flood walls.

Three of the six reactors on the site were operational at the time and suffered core meltdowns. Three of the reactors also exploded after excessive hydrogen gas built up in containment buildings.

"This plant was protected from baby tsunamis, not large tsunamis," Lochbaum said.

Backup equipment and emergency generators were flooded out and rendered inoperable. Sea water within a stone's throw from the overheating reactors couldn't be pumped in to cool them off.

"Within three hours, the three operating cores melted down," he said.

Lochbaum then showed a Nuclear Regulatory Committee memo dated July 2010 — nearly a year before Fukushima — that he said he received in an unmarked envelope at his post office box in Tennessee. This memo listed six plants nationwide at high risk from flooding.

The Oconee Nuclear Station was one of them.

Another one of the plants, Fort Calhoun in Nebraska, was inundated by flood waters from the Missouri River after heavy rainfall in June 2011. Fortunately, the plant had been closed since April 2011.

The Oconee plant is 12 miles due south of Jocassee Dam, which has a chance of one in 3,571 years of failing, according to federal estimates Lochbaum cited.

"What are the chances of the three reactors failing if the dam failed?" Lochbaum said. "According to the NRC, it's 100 percent."

The reactors would have core meltdown in eight to nine hours, Lochbaum said, and containment of the radiation would fail after about 60 hours. The public would have time to be evacuated, he said, but weather patterns would affect the direction in which the radiation would float through the air.

The chances of an earthquake and tsunami like that seen at Fukushima, Lochbaum said, was one in 1,000 years — three and a half times greater than a Jocassee Dam break.

"Our country has 34 dams in harm's way," Lochbaum said. "If they all operate another 20 years and all have similar chance of failure, there's a 50-50 chance that one dam somewhere will fail."

Duke Energy has already taken measures to detect any future problems at Jocassee. This includes the installation of cameras to monitor the dam at all times.

Reached last week at Duke, the site's vice president, Preston Gillespie, said Duke has also installed better monitoring equipment in its spent-fuel-rod pools to track the level of water at all depths there.

Duke also has plans in the works for a taller wall around its backup control room and a diversion wall to direct flood waters around the plant.

"The bad news is those plans were supposed to be completed by November 2011," Lochbaum said. "After Fukushima, there was a five-year delay."

Officials with the NRC said that lessons learned from Fukushima have necessitated a closer look at safety changes across the country. A couple of the audience members raised that argument with Lochbaum on Wednesday, saying Duke ought to take a careful, if slower approach, to known problems with the new data coming out of Japan.

"I don't see where the negligence is," one audience member said. "Now that they know of more problems at Fukushima, five years seems fine."

Lochbaum said the probability of a dam break and flood at Jocassee, like the large tsunami at Fukushima, has been deemed too remote in past assessments to build in safety precautions. He called that "undue optimism" and repeated his call for a more urgent response. The five-year time frame could, without prodding federal regulators, turn into a decade or two decades.

"If I could get five years in writing, I would stop squawking," Lochbaum said. "But that five years is a promise they never keep. Time and time again, there are issues and when the industry says they need more time, the NRC always says OK."